U.S. patent application number 15/538903 was filed with the patent office on 2017-11-30 for impedance matching method and device for pulsed radio frequency power supply.
The applicant listed for this patent is BEIJING NAURA MICROELECTRONICS EQUIPMENT CO., LTD. Invention is credited to Xiaoyang CHENG.
Application Number | 20170345621 15/538903 |
Document ID | / |
Family ID | 56355453 |
Filed Date | 2017-11-30 |
United States Patent
Application |
20170345621 |
Kind Code |
A1 |
CHENG; Xiaoyang |
November 30, 2017 |
IMPEDANCE MATCHING METHOD AND DEVICE FOR PULSED RADIO FREQUENCY
POWER SUPPLY
Abstract
An impedance matching method and device for a pulsed RF power
supply are provided. The impedance matching method includes: a
coarse adjustment step: performing adjustment based on a current
load impedance to make a current reflection coefficient |.GAMMA.|
no greater than an ignition reflection coefficient |.GAMMA.t|, and
setting a current position as an ignition position; a fine
adjusting step: keeping the ignition position unchanged, performing
real-time adjustment based on the current load impedance to realize
impedance matching, and setting a current position as a matching
position; and a switching step: after impedance matching is
realized for the first time, switching between the ignition
position and the matching position in different pulse time
durations of each subsequent pulse period to realize impedance
matching in different pulse periods. The impedance matching method
and device may improve matching efficiency, process stability and
utilization of the pulsed RF power supply.
Inventors: |
CHENG; Xiaoyang; (Beijing,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BEIJING NAURA MICROELECTRONICS EQUIPMENT CO., LTD |
Beijing |
|
CN |
|
|
Family ID: |
56355453 |
Appl. No.: |
15/538903 |
Filed: |
April 29, 2015 |
PCT Filed: |
April 29, 2015 |
PCT NO: |
PCT/CN2015/077779 |
371 Date: |
June 22, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/02 20130101;
H01J 37/32146 20130101; H05H 1/46 20130101; H03H 7/40 20130101;
H05H 2001/4682 20130101; H01J 37/32183 20130101; H01J 37/32
20130101 |
International
Class: |
H01J 37/32 20060101
H01J037/32; H01L 21/02 20060101 H01L021/02; H03H 7/40 20060101
H03H007/40; H05H 1/46 20060101 H05H001/46 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 6, 2015 |
CN |
201510004040.8 |
Claims
1. An impedance matching method for a pulsed RF power supply,
comprising: a coarse adjustment step: performing adjustment based
on a current load impedance to make a current reflection
coefficient |.GAMMA.| no greater than an ignition reflection
coefficient |.GAMMA.t|, and setting a current position to be an
ignition position; a fine adjustment step: keeping the ignition
position to be unchanged, performing adjustment in real time based
on the current load impedance to realize impedance matching, and
setting the current position to be a matching position; and a
switching step: switching between the ignition position and the
matching position in different pulse time durations of each
subsequent pulse period after impedance matching is realized for a
first time, thereby realizing impedance matching in different pulse
periods.
2. The impedance matching method according to claim 1, wherein the
impedance matching method comprises: Step 1: determining, in real
time, whether or not the current reflection coefficient |.GAMMA.|
is no greater than the ignition reflection coefficient |.GAMMA.t|;
if the current reflection coefficient |.GAMMA.| is determined to be
greater than the ignition reflection coefficient |.GAMMA.t|, Step 2
is executed, otherwise, the fine adjustment step is executed; and
Step 2: performing the coarse adjustment step in real time based on
the current load impedance, and returning to Step 1.
3. The impedance matching method according to claim 1, wherein
before the coarse adjusting step, the method further comprises:
determining whether or not a current moment is in a high voltage
level period of a pulse period when matching has not been realized;
if the current moment is determined to be in the high voltage level
period of the pulse period when matching has not been realized,
executing the coarse adjustment step; otherwise, maintaining the
current position to be unchanged.
4. The impedance matching method according to claim 3, wherein when
the current moment is determined to be in the high voltage level
period of the pulse period when the matching has not been realized,
the pulsed RF power supply uses a frequency-sweep mode to perform
automatic impedance matching.
5. The impedance matching method according to claim 1, wherein the
fine adjustment step further comprises: storing the matching
position when impedance matching is realized.
6. The impedance matching method according to claim 1, wherein the
switching step comprises: after impedance matching is realized for
the first time, switching from the ignition position to the
matching position in a high voltage level period of each subsequent
pulse period, and switching from the matching position to the
ignition position in a low voltage level period of each subsequent
pulse period.
7. An impedance matching device for a pulsed RF power supply
configured to match a load impedance of the pulsed RF power supply
with a characteristic impedance of the pulsed RF power supply,
wherein the device comprises a coarse adjusting unit, a fine
adjusting unit, and a switching unit, wherein: the coarse adjusting
unit is configured to adjust, based on a current load impedance, a
current reflection coefficient |.GAMMA.| to be no greater than an
ignition reflection coefficient |.GAMMA.t|, and set a current
position as a ignition position; the fine adjusting unit is
configured to maintain the ignition position to be unchanged when
the current reflection coefficient |.GAMMA.| is no greater than the
ignition reflection coefficient |.GAMMA.t|, perform adjustment in
real time based on the current load impedance to realize impedance
matching, and set a current position as a matching position; and
the switching unit is configured to switch between the ignition
position and the matching position in different pulse time
durations of each subsequent pulse period after impedance matching
is realized for a first time, thereby realizing impedance matching
in different pulse periods.
8. The impedance matching device according to claim 7, further
comprising a control module, a reflection coefficient determination
module, and a calculation module, wherein: the calculation module
is configured to calculate, in real time, the current load
impedance and the current reflection coefficient |.GAMMA.| of the
pulsed RF power supply, send the current load impedance to the
coarse adjusting unit and the fine adjusting unit, and send the
current reflection coefficient |.GAMMA.| to the reflection
coefficient determination module; the reflection coefficient
determination module is configured to determine whether or not the
current reflection coefficient |.GAMMA.| is no greater than the
ignition reflection coefficient |.GAMMA.t|, if the current
reflection coefficient |.GAMMA.| is determined to be greater than
the ignition reflection coefficient |.GAMMA.t|, send a first
identification signal to the control module, otherwise, send a
second identification signal to the control module; and the control
module is configured to trigger the coarse adjusting unit upon
receival of the first identification signal sent from the
reflection coefficient determination module, and trigger the fine
adjusting unit upon receival of the second identification signal
sent from the reflection coefficient determination module.
9. The impedance matching device according to claim 8, wherein the
coarse adjusting unit comprises an adjustable capacitor and/or an
adjustable inductor, wherein: the coarse adjusting unit is
configured to adjust, in real time, a position of the adjustable
capacitor and/or the adjustable inductor based on the current load
impedance sent from the calculation module to adjust the current
reflection coefficient |.GAMMA.| to be no greater than the ignition
reflection coefficient |.GAMMA.t|, and set a current position of
the adjustable capacitor and/or the adjustable inductor as the
ignition position.
10. The impedance matching device according to claim 8, wherein the
fine adjusting unit comprises a fixed capacitor and/or a fixed
inductor, and an on-off switch connected in series therewith,
wherein: the fine adjusting unit is configured to control, in real
time, the on-off switch to be on or off based on the current load
impedance sent from the calculation module to realize impedance
matching, and set a current state of the on-off switch to be a
matching on-off state.
11. The impedance matching device according to claim 7, wherein the
device further comprises: a pulse period determination module,
configured to determine whether or not a current moment is in a
high voltage level period of a pulse period when matching has not
been realized, if the current moment is determined to be in the
high voltage level period of the pulse period when matching has not
been realized, trigger the coarse adjusting unit, otherwise,
maintain the current position to be unchanged.
12. The impedance matching device according to claim 7, wherein the
device further comprises: a storage module, configured to store the
matching position when the fine adjusting unit performs adjustment
in real time based on the current load impedance to realize
impedance matching.
13. The impedance matching device according to claim 7, wherein the
switching unit is configured to, after impedance matching is
realized for the first time, switch from the ignition position to
the matching position in a high voltage level period of each
subsequent pulse period and switch from the matching position to
the ignition position in a low voltage level period of each
subsequent pulse period.
Description
FIELD OF THE DISCLOSURE
[0001] The present disclosure relates to the technical field of
semiconductor device manufacturing and, more particularly, relates
to an impedance matching method and device for a pulsed radio
frequency (RF) power supply.
BACKGROUND
[0002] A semiconductor processing apparatus often excites a process
gas in a reaction chamber to form plasma by applying the RF energy
provided by the RF power supply into the reaction chamber with a
high vacuum environment. The plasma includes a large amount of
active particles, such as electrons, ions, excited atoms,
molecules, and free radicals. The active particles react physically
and/or chemically with a surface of a wafer exposed to the plasma
environment, thereby fulfilling etching, deposition, or other
processes of the wafer. As the integrated circuit further develops,
the existing technology cannot meet requirements for an etching
process with a dimension of 22 nm or less. As such, a pulsed RF
power supply is used as a plasma excitation source to reduce the
plasma induced damage caused by continuous-wave RF energy and
enlarge the process adjustment method and the process window.
Currently, a key factor that restricts the development of the
pulsed RF power supply as the plasma excitation source is the
impedance matching technique for the pulsed RF power supply.
Impedance matching refers to matching the load impedance of the
pulsed RF power supply with the characteristic impedance
(generally, 50 ohms) of the pulsed RF power supply. The common
pulsed frequency range of the pulsed RF power supply is
100.about.100 kHz, and the range of the duty cycle is
10%.about.90%. Accordingly, each pulse width is only a few
milliseconds. However, by using the existing impedance matching
device that relies on the method of mechanical adjustment,
impedance matching can hardly be fulfilled within such a few
milliseconds, resulting in a low matching accuracy and a high
reflection power (generally, 20%) of the pulsed RF power supply.
Thus, the utilization of the pulsed RF power supply is poor.
[0003] Accordingly, an impedance matching device shown in FIG. 1 is
used in existing technologies. The impedance matching device
primarily uses the method of electronic adjustment, and
occasionally uses the method of mechanical adjustment. Referring to
FIG. 1, the impedance matching device 10 includes a control unit
11, an execution unit 12, and a matching network 13. The pulsed RF
power supply 14 has a frequency-sweep function and sends a pulse
synchronous signal to the control unit 11, and the pulse
synchronous signal is shown in FIG. 2. During a high voltage level
period, the pulsed RF power supply 14 is modulated with a RF power
signal, and during a low voltage level period, the pulsed RF power
supply 14 is not modulated with a RF power signal. An impedance
adjustable element is disposed in the matching network 13; the
pulsed RF power supply 14 automatically performs frequency-sweep
matching in a high voltage level period (i.e., the pulse frequency
with the maximum output power is obtained by automatic adjustment
based on the load impedance of the pulsed RF power supply 14); the
control unit 11 acquires a current pulse frequency of the pulsed RF
power supply 14 in the high voltage level period of each pulse
period in real-time based on the pulse synchronous signal,
calculates a current load impedance of the pulsed RF power supply
14 according to the current pulse frequency, a circuit structure of
the matching network 13 and a current position of the impedance
adjustable element of the matching network 13, and determines
whether the current load impedance matches the characteristic
impedance of the pulsed RF power supply 14. If the current load
impedance matches the characteristic impedance of the pulsed RF
power supply 14, the current position of the impedance adjustable
element is maintained at the low voltage level of the current pulse
period. That is, the matching position is maintained. If the
current load impedance does not match the characteristic impedance
of the pulsed RF power supply 14, the execution unit 12 is
controlled to adjust the position of the impedance adjustable
element when the current pulse period is at low voltage levels,
thereby performing impedance matching by adjusting the load
impedance of the pulsed RF power supply 14.
[0004] FIG. 3 is a structural schematic diagram of a reaction
chamber using an existing impedance matching device. Referring to
FIG. 3, an induction coil 21 is disposed above the top of the
reaction chamber 20, and the induction coil 21 is electrically
connected to a first RF power supply 23 via a first impedance
matching device 22. An electrostatic chuck 24 for bearing a wafer S
is disposed in a bottom region inside the reaction chamber 20, and
the electrostatic chuck 24 is electrically connected to a second RF
power supply 26 via a second impedance matching device 25. The
first RF power supply 23 adopts a continuous-wave signal output
mode, namely, the first RF power supply 23 continuously outputs a
RF power signal. The second RF power supply 26 is a pulsed RF power
supply, the frequency of the RF power signal generated by the
second RF power supply is 13.56 MHz, the frequency of the pulse
synchronous signal is 100 Hz, and the duty cycle is 90%. The second
impedance matching device 25 uses the impedance matching device
illustrated in FIG. 1.
[0005] Under the aforementioned conditions, FIG. 4 is a schematic
diagram of the matching status of the second impedance matching
device 25 at different time points in an impedance matching
process. Referring to FIG. 4, specifically, during a first pulse
period: in the high voltage level period, the RF power supply 26
starts automatic frequency-sweep matching and remains in a status
of "under matching", that is, the impedance matching is not
realized; in the low voltage level period, the control unit 11
performs impedance matching by controlling the execution unit 12 to
adjust the position of the impedance adjustable element. During a
second pulse period: in the high voltage level period, the RF power
supply 26 starts the automatic frequency-sweep matching, and after
a period of T, the status of "under matching" is changed to a
status of "matched", namely, the impedance matching not being
realized is changed into the impedance matching is realized; in the
low voltage level period, the matching position remains unchanged.
The matching processes of a third pulse period and a subsequent
pulse period are similar to the matching process of the second
pulse period, and are not repeated herein.
[0006] Correspondingly, FIG. 5 is an impedance changing trajectory
of the load impedance of the second RF power supply in the
impedance matching process represented by the Smith chart.
Referring to FIG. 5, the most central point of the Smith chart
represents one matched resistance value (50 ohms), and the position
where the most central point is located is called an impedance
matching point. In such Smith chart, the impedance matching process
is actually a moving process of the load impedance from an edge
position of the chart towards the most central position of the
chart, and the moving process specifically includes traversing the
impedance zone 1, the impedance zone 2, the impedance zone 3, and
the impedance zone 4 sequentially.
[0007] When the pulsed RF power supply 26 is not turned on, the
load impedance is the impedance induced by an interference signal
and is shown as the impedance zone 1 outside of the circle in the
Smith chart. After the pulsed RF power supply 26 is turned on, in
the high voltage level period of the first pulse period of the
impedance matching process, the current load impedance is initially
located in the impedance zone 2, the impedance value is
approximately 6.angle.-86.degree., and at this moment, the pulsed
RF power supply 26 has not realized ignition in the reaction
chamber. As the pulsed RF power supply 26 performs automatic
frequency-sweep matching, the current load impedance moves
gradually from the impedance zone 2 towards the impedance matching
position but has not reached the impedance matching point. In the
low voltage level period of the first pulse period, no impedance
matching is performed, and at this moment, the load impedance is
located in the impedance zone 4 outside of the Smith circle and is
the coupled signal impedance of the induction coil 21. During the
second pulse period of the impedance matching process, in the high
voltage level period, because the impedance adjustable element is
adjusted in the low voltage level period of the first pulse period,
the load impedance is, at the very beginning, located in a
non-ignition impedance zone of the impedance zone 2 that moves a
certain distance towards the impedance matching point. Accordingly,
the pulsed RF power supply 26 does not realize ignition at first.
As the pulsed RF power supply 26 performs automatic frequency-sweep
matching, the current load impedance moves to the impedance zone 3,
the impedance value is approximately 40.angle.25.degree., and by
then, impedance matching is basically realized. In the low voltage
level period of the second pulse period, the load impedance is the
same located in the impedance zone 4. The movement processes of the
load impedance corresponding to the third pulse period and the
subsequent pulse period are similar to the movement process of the
load impedance corresponding to the second pulse period, and are
not repeated herein.
[0008] In practical applications, the following technical issues
often exist when the aforementioned existing impedance matching
device is used to perform impedance matching on the pulsed RF power
supply. Because the function of the pulsed RF power supply in a
processing process is to excite the process gas in the reaction
chamber to form plasma, and the load impedance of the pulsed RF
power supply when the reaction chamber is ignited is different from
the load impedance of the pulsed RF power supply when the impedance
matching is realized. Thus, after the impedance matching is
realized for the first time, in the high voltage level period of
each subsequent pulse period, the pulsed RF power supply needs to
first realize the ignition of the reaction chamber and then realize
the impedance matching. That is, in the high voltage level period
of each subsequent pulse period, to realize the ignition of the
process gas, the load impedance needs to be adjusted from the
matched load impedance value obtained in the previous pulse period
to ignition load impedance value. After ignition, the automatic
frequency-sweep matching process shown in FIG. 4 and FIG. 5 may be
used to match the load impedance until the load impedance value
that realizes matching is achieved. In other words, when using the
existing impedance matching device to realize impedance matching,
the high voltage level period of each subsequent pulse period needs
to undergo a relatively long automatic frequency-sweep matching
period T. Thus, the matching efficiency is low, resulting in poor
processing stability and low utilization of the pulsed RF power
supply.
[0009] Therefore, an impedance matching method and device thereof
that can implement rapid impedance matching for a pulsed RF power
supply are urgently needed.
SUMMARY OF THE DISCLOSURE
[0010] Directed to solving the technical issues existing in the
prior art, the present disclosure provides an impedance matching
device and a semiconductor processing apparatus that may rapidly
realize the impedance matching for the pulsed RF power supply.
Accordingly, the processing stability may be enhanced, and the
utilization of the RF energy of the pulsed RF power supply may be
improved.
[0011] To solve the technical issues existing in the prior art, the
present disclosure provides an impedance matching method for a
pulsed RF power supply, and the impedance matching method includes
the following steps: a coarse adjustment step, where adjustment is
performed based on the current load impedance, such that the
current reflection coefficient |.GAMMA.| is no greater than an
ignition reflection coefficient |.GAMMA.t|, and a current position
is set as an ignition position; a fine adjustment step, where the
ignition position remains unchanged, real-time adjustment is
performed to realize impedance matching based on the current load
impedance, and a current position is set as a matching position;
and a switching step, where after the impedance matching is
realized for the first time, in different pulse time durations of
each subsequent pulse period, switching is performed between the
ignition position and the matching position, thereby realizing
impedance matching in different pulse periods.
[0012] More specifically, the impedance matching method includes
the following steps:
[0013] Step 1: determining, in real time, whether or not the
current reflection coefficient |.GAMMA.| is no greater than the
ignition reflection coefficient |.GAMMA.t|. If the current
reflection coefficient |.GAMMA.| is determined to be greater than
the ignition reflection coefficient |.GAMMA.t|, Step 2 is executed,
otherwise, the fine adjustment step is executed; and
[0014] Step 2: the coarse adjustment step is executed in real time
based on the current load impedance, and Step 1 is returned to.
[0015] Further, before the coarse adjustment step, the method
further includes: determining whether or not a current time point
(a current moment) is within a high voltage level period of the
pulse period when the matching has not been realized. If the
current time point is within a high voltage level period of the
pulse period when the matching has not been realized, the coarse
adjustment step is executed; otherwise, the current position
remains unchanged.
[0016] Further, when the current time period is determined to be
within the high voltage level period of the pulse period given that
the matching has not been realized, the pulsed RF power supply uses
a frequency-sweep mode to perform automatic impedance matching.
[0017] Further, the fine adjustment step further includes: storing
the matching position when the impedance matching is realized.
[0018] Further, the switching step includes: after the impedance
matching is realized for the first time, switching from the
ignition position to the matching position in the high voltage
level period of each subsequent pulse period, and switching from
the matching position to the ignition position in the low voltage
level period of each subsequent pulse period.
[0019] As another aspect, the present disclosure further provides
an impedance matching device for a pulsed RF power supply that is
configured to realize matching between the load impedance of the
pulsed RF power supply and the characteristic impedance of the
pulsed RF power supply. The device includes: a coarse adjusting
unit, a fine adjusting unit and a switching unit. The coarse
adjusting unit is configured to adjust, according to a current load
impedance, a current reflection coefficient |.GAMMA.| to be no
greater than the ignition reflection coefficient |.GAMMA.t|, and
set a current position as an ignition position. The fine adjusting
unit is configured to keep the ignition position to be unchanged
when the current reflection coefficient |.GAMMA.| is no greater
than the ignition reflection coefficient |.GAMMA.t|, perform
real-time adjustment based on the current load impedance to realize
impedance matching, and set the current position as a matching
position. The switching unit is configured to switch between the
ignition position and the matching position in different pulse time
durations of each subsequent pulse period after the impedance
matching is realized for the first time, such that impedance
matching in different pulse periods may be realized.
[0020] Further, the device further includes: a control module, a
reflection coefficient determination module and a calculation
module. The calculation module is configured to calculate, in real
time, the current load impedance and the current reflection
coefficient |.GAMMA.| of the pulsed RF power supply, send the
current load impedance to the coarse adjusting unit and the fine
adjusting unit, and send the current reflection coefficient
|.GAMMA.| to the reflection coefficient determination module. The
reflection coefficient determination module is configured to
determine whether or not the current reflection coefficient
|.GAMMA.| is no greater than the ignition reflection coefficient
|.GAMMA.t|.I If the current reflection coefficient |.GAMMA.| is
determined to be greater than the ignition reflection coefficient
|.GAMMA.t|, a first identification signal is sent to the control
module; otherwise, a second identification signal is sent to the
control module. The control module is configured to trigger the
coarse adjusting unit upon receival of the first identification
signal sent from the reflection coefficient determination module,
and trigger the fine adjusting unit upon receival of the second
identification signal sent from the reflection coefficient
determination module.
[0021] Further, the coarse adjusting unit includes an adjustable
capacitor and/or an adjustable inductor. The coarse adjusting unit
is configured to adjust, in real time, a position of the adjustable
capacitor and/or the adjustable inductor according to the current
load impedance sent from the calculation module, such that the
current reflection coefficient |.GAMMA.| is adjusted to be no
greater than the ignition reflection coefficient |.GAMMA.t|.
Further, the coarse adjusting unit set the current position of the
adjustable capacitor and/or the adjustable inductor as the ignition
position.
[0022] Further, the fine adjusting unit includes a fixed capacitor
and/or a fixed inductor, and an on-off switch connected in series
therewith. The fine adjusting unit is configured to control, in
real time, the on or off of the on-off switch based on the current
load impedance sent from the calculation module to realize the
impedance matching, and set the current state of the on-off switch
to be a matching on-off state.
[0023] Further, the device further includes a pulse period
determination module configured to determine whether or not a
current time point is in a high voltage level period of the pulse
period when the matching has not been realized. If yes, the coarse
adjusting unit is triggered, otherwise, the current position
remains unchanged.
[0024] Further, the device further includes a storage module
configured to store the matching position when the fine adjusting
unit performs real-time adjustment based on the current load
impedance to realize impedance matching.
[0025] Further, the switching unit is configured to, after the
impedance matching is realized for the first time, switch from the
ignition position to the matching position in the high voltage
level period of each subsequent pulse period and switch from the
matching position to the ignition position in the low voltage level
period of each subsequent pulse period.
[0026] The present disclosure has the following beneficial
effects.
[0027] In the impedance matching method for a pulsed RF power
supply provided by the present disclosure, by virtue of the coarse
adjustment step, adjustment is performed based on the current load
impedance, such that the current reflection coefficient |.GAMMA.|
is no greater than the ignition reflection coefficient |.GAMMA.t|,
and the current position is set as the ignition position. Further,
by virtue of the fine adjustment step, the ignition position
remains unchanged, real-time adjustment is performed to realize
impedance matching based on the current load impedance, and the
current position is set as the matching position. Further by virtue
of the switching step, after the impedance matching is realized for
the first time, in different pulse time durations in each
subsequent pulse period, switching is performed between the
ignition position and the matching position. More specifically, in
the high voltage level period of each subsequent pulse period, the
initial position is switched to the matching position, and in the
low voltage level period of each subsequent pulse period, the
matching position is switched to the ignition position.
Accordingly, ignition may be realized directly in the high voltage
level period of the next pulse period, and the re-matching may be
realized by switching the ignition position to the matching
position. Thus, the matching time of each subsequent pulse period
is the switching time between the ignition position and the
matching position. As such, different from the matching time of
each subsequent pulse period in the prior art being a relatively
long time required by the automatic frequency sweeping and repeated
adjustments of the load impedance to realize the matching, the
processing stability may be enhanced, and utilization of the pulsed
RF power supply may be improved.
[0028] In the impedance matching device for a pulsed RF power
supply provided by the present disclosure, by virtue of the coarse
adjusting unit and based on the current load impedance, the current
reflection coefficient |.GAMMA.| is adjusted to be no greater than
the ignition reflection coefficient |.GAMMA.t|, and the current
position is set as the ignition position. When the current
reflection coefficient |.GAMMA.| is no greater than the ignition
reflection coefficient |.GAMMA.t|, the fine adjusting unit keeps
the ignition position unchanged, performs real-time adjustment to
realize impedance matching based on the current load impedance, and
sets the current position to be the matching position. Further, the
switching unit switches between ignition position and the matching
position in different pulse time durations of each subsequent pulse
period after the impedance matching is realized for the first time.
More specifically, the switching unit switches from the initial
position to the matching position in the high voltage level period
of each subsequent pulse period, and switches from the matching
position to the ignition position in the low voltage level period
of each subsequent pulse period, thereby ensuring that the ignition
can be realized directly in a high voltage level period of a next
pulse period, and re-matching may be realized by switching the
ignition position to the matching position. As such, different from
the matching time of each subsequent pulse period in the prior art
being a relatively long time required by the automatic frequency
sweeping and repeated adjustments of the load impedance to realize
the matching, the processing stability may be enhanced, and
utilization of the pulsed RF power supply may be improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a principle block diagram for applying an existing
impedance matching device;
[0030] FIG. 2 is a waveform diagram of a pulse synchronous signal
of a pulsed RF power supply;
[0031] FIG. 3 is a structural schematic diagram of a reaction
chamber using an existing impedance matching device;
[0032] FIG. 4 is a schematic diagram illustrating matching statuses
of a second impedance matching device at different time points
during a impedance matching process;
[0033] FIG. 5 is a trajectory graph of a load impedance of a second
RF power supply during an impedance matching process
correspondingly reflected in the Smith chart;
[0034] FIG. 6 is a flow chart of an impedance matching method for a
pulsed RF power supply according to a first embodiment of the
present disclosure;
[0035] FIG. 7 is a principle block diagram of an impedance matching
device for a pulsed RF power supply according to a second
embodiment of the present disclosure;
[0036] FIG. 8 is a schematic diagram of a coarse adjusting unit and
a fine adjusting unit in FIG. 7;
[0037] FIG. 9 is an operational flow chart of an impedance matching
device shown in FIG. 7;
[0038] FIG. 10 is a schematic diagram illustrating matching
statuses of an impedance matching device when impedance matching is
performed at different time points under a situation where a
current reflection coefficient |.GAMMA.| is greater than an
ignition reflection coefficient |.GAMMA.t|;
[0039] FIG. 11 is a trajectory graph of a load impedance of a
pulsed RF power supply during an impedance matching process
correspondingly reflected in the Smith chart; and
[0040] FIG. 12 is a schematic diagram illustrating matching
statuses of an impedance matching device when impedance matching is
performed at different time points under a situation where a
current reflection coefficient |.GAMMA.| is no greater than an
ignition reflection coefficient |.GAMMA.t|.
DETAILED DESCRIPTION
[0041] To make those skilled in the relevant art better understand
technical solutions of the present disclosure, an impedance
matching method and device thereof for a pulsed RF power supply
provided by the present disclosure will be described in detail
hereinafter with reference to the accompanying drawings.
[0042] FIG. 6 is a flow chart of an impedance matching method for a
pulsed RF power supply provided by a first embodiment of the
present disclosure. Referring to FIG. 6, the impedance matching
method for a pulsed RF power supply provided by a first embodiment
of the present disclosure is used for matching a load impedance of
the pulsed RF power supply with a characteristic impedance (e.g.,
50 ohms) of the pulsed RF power supply, and the impedance matching
method includes the following steps.
[0043] A coarse adjustment step: performing adjustment based on a
current load impedance, such that a current reflection coefficient
|.GAMMA.| is no greater than an ignition reflection coefficient
|.GAMMA.t|, and setting a current position as an ignition
position.
[0044] The physical meaning of the reflection coefficient |.GAMMA.|
of a pulsed RF power supply is a ratio of a reflected voltage wave
to an incident voltage wave at a load impedance point of the pulsed
RF power supply. The ignition reflection coefficient |.GAMMA.t|
refers to the reflection coefficient |.GAMMA.| corresponding to the
load impedance when the pulsed RF power supply realizes ignition in
a reaction chamber. For a certain processing process, the load
impedance and the reflection coefficient |.GAMMA.| of the pulsed RF
power supply when the reaction chamber realizes ignition are
constants. However, because parameters such as the chamber pressure
and the process gas in different processing processes have certain
influence on the pulsed RF power supply when realizing ignition in
the reaction chamber, the load impedance and the reflection
coefficient |.GAMMA.| of the pulsed RF power supply when realizing
ignition in the reaction chamber often vary in different processing
processes.
[0045] Here, FIG. 5 needs to be further illustrated. In FIG. 5, the
impedance zone 2 indicates a load impedance value when a process
gas at the beginning of a high voltage level period is not ignited,
and the impedance zone 3 indicates a load impedance value when the
process gas is ignited and stabilized and impedance matching is
basically realized in the high voltage level period. Between the
impedance zone 2 and the impedance zone 3, a load impedance value
(not shown in the drawings), exists in the corresponding high
voltage level period at the moment when the process gas is ignited,
and such load impedance value is close to the impedance zone 3.
[0046] Therefore, the object of the coarse adjustment step
according to the present disclosure is to find a load impedance
value when an impedance matching state is nearly achieved. That is,
in a decreasing process of the current reflection coefficient
|.GAMMA.| from a value greater than the ignition reflection
coefficient |.GAMMA.t| to a value equal to the ignition reflection
coefficient |.GAMMA.t|, the current load impedance value gradually
approaches the load impedance value in the impedance matching
state. That is, the current load impedance value gradually moves
from a range of the impedance zone 2 towards a range of the
impedance zone 3 in FIG. 5. It is specified that when the current
reflection coefficient |.GAMMA.| is no greater than the ignition
reflection coefficient |.GAMMA.t|, the current load impedance value
is the load impedance value at the instant moment when the process
gas is ignited, and thus the position of each component in the
current condition is set as the ignition position. By then, the
impedance matching has not been realized.
[0047] A fine adjusting step: keeping the ignition position to be
unchanged, performing adjustment in real time based on the current
load impedance to realize the impedance matching, and setting the
current position as a matching position.
[0048] After the coarse adjustment step, given each component at
the ignition position remains unchanged, the fine adjusting step is
performed until the load impedance value when impedance matching is
realized is found. That is, the current load impedance value is
adjusted to be located in the impedance zone 3 in FIG. 5, and the
position of each component at this moment is stored as the matching
position.
[0049] After the aforementioned two steps, the present disclosure
obtains two positions, namely, the ignition position and the
matching position, and the impedance matching for the current
pulsed RF power supply is fulfilled simultaneously for the first
time.
[0050] A switching step: after the impedance matching is realized
for the first time, in different pulse time durations of each
subsequent pulse period (i.e., high voltage level period and low
voltage level period), switching is performed between the ignition
position and the matching position to realize impedance matching in
different pulse periods. Specifically, during each pulse period
after the first impedance matching, in the initial stage of the
high voltage level period, each component is at the ignition
position to allow the process gas to be ignited; and then each
component is switched from the status of ignition position to the
status of matching position, thereby realizing impedance
matching.
[0051] As such, when at the ignition position and the current
reflection coefficient |.GAMMA.| is no greater than the ignition
reflection coefficient |.GAMMA.t|, the pulsed RF power supply may
realize the ignition of the process gas. Later, the pulsed RF power
supply may realize impedance matching when in the matching
position. Thus, in the switching step, in the high voltage level
period of each subsequent pulse period after the impedance matching
is realized for the first time, repeat matching may no longer be
needed as that described in existing technologies where load
impedance is adjusted repeatedly via automatic frequency sweeping,
and impedance matching may be realized by switching the ignition
position to the matching position. Further, in the low voltage
level period of each subsequent pulse period, each component may be
switched from the matching position to the ignition position.
Accordingly, ignition may be ensured to be realized directly in the
high voltage level period of the next pulse period, and re-matching
may be realized by switching the ignition position to the matching
position. Thus, in one embodiment, in the high voltage level period
of each subsequent pulse period after the impedance matching is
realized for the first time, the matching time is a switching time
during which the ignition position is switched to the matching
position. The matching time is a period of time that a matching
process takes to switch an unmatched state to a matched state. By
comparing the prior art and the disclosed embodiments, in each
subsequent pulse period after the impedance matching is realized
for the first time, the matching time in the prior art is
relatively long because a relatively long time is spent on
automatic frequency sweeping and repeated adjustment of the load
impedance to realize matching. However, in embodiments of the
present disclosure, repeat adjustment of the load impedance is no
longer needed, and matching may be realized by switching each
component from the ignition position to the matching position.
Thus, the matching time is short, and the matching efficiency is
high, such that the stability of the process and the utilization of
the pulsed RF power supply may be improved.
[0052] More specifically, in one embodiment, the impedance matching
method includes the following steps:
[0053] Step S1: determining, in real time, whether or not the
current reflection coefficient |.GAMMA.| is no greater than the
ignition reflection coefficient |.GAMMA.t|. If the current
reflection coefficient |.GAMMA.| is determined to be greater than
the ignition reflection coefficient |.GAMMA.t|, Step S2 is
executed, otherwise, the fine adjustment step is executed.
[0054] Step S2: performing the coarse adjustment step in real time
based on the current load impedance, and returning to Step S1.
[0055] Through Step S1 and Step S2, real-time determination and
adjustment may be realized until the current reflection coefficient
|.GAMMA.| is no greater than the ignition reflection coefficient
|.GAMMA.t|.
[0056] Preferably, before the coarse adjustment step, the method
further includes: determining whether or not a current moment is in
a high voltage level period of the pulse period when matching is
not realized. If yes, the coarse adjustment step is executed;
otherwise, the current moment is in the low voltage level period of
the pulse period and the current position remains unchanged. As
such, the disclosed impedance matching method may perform the
coarse adjustment step only in the high voltage level period of a
current pulse period when the matching has not been realized, and
no operation is performed in the low voltage level period. Thus,
"blind adjustment" may be avoided compared to the prior art in
which the execution mechanism is controlled to adjust, in the low
voltage level period, the impedance adjustable element based on the
load impedance at the last time point of the high voltage level
period. Accordingly, the occurrence of the over-adjustment
phenomenon may be avoided, thereby improving the matching
efficiency when the impedance matching is realized for the first
time.
[0057] Further and preferably, when the current moment is
determined to be in the high voltage level period of the pulse
period when matching has not been realized, the pulsed RF power
supply uses the frequency-sweep mode to perform automatic impedance
matching. That is, the pulsed RF power supply automatically adjusts
the pulse frequency to perform matching, which may not only further
enhance the matching efficiency but also improve the matching
accuracy.
[0058] Further, the fine adjustment step further includes: storing
the matching position when the impedance matching is realized.
[0059] FIG. 7 is a principle block diagram of an impedance matching
device for a pulsed RF power supply provided by a second embodiment
of the present disclosure. Referring to FIG. 7, the impedance
matching device is configured to match a load impedance of the
pulsed RF power supply with a characteristic impedance (e.g., 50
ohms) of the pulsed RF power supply. The impedance matching device
includes a coarse adjusting unit, a fine adjusting unit, and a
switching unit. The coarse adjusting unit is configured to perform
adjustment based on a current load impedance, such that a current
reflection coefficient |.GAMMA.| is no greater than the ignition
reflection coefficient |.GAMMA.t|, and set a current position as an
ignition position. The physical meaning of the reflection
coefficient |.GAMMA.| of the pulsed RF power supply is a ratio of a
reflected voltage wave to an incident voltage wave at a load
impedance point of the pulsed RF power supply, and the ignition
reflection coefficient |.GAMMA.t| refers to the reflection
coefficient |.GAMMA.| corresponding to the load impedance of the
pulsed RF power supply when ignition is realized in a reaction
chamber. For a certain processing process, the load impedance and
the reflection coefficient |.GAMMA.| of the pulsed RF power supply
when ignition is realized in the reaction chamber are constants.
However, because parameters such as the chamber pressure and the
process gas in different processing processes have certain
influence on the the pulsed RF power supply to realize ignition in
the reaction chamber, the load impedance and the reflection
coefficient |.GAMMA.| of the pulsed RF power supply when ignition
is realized in the reaction chamber often vary in different
processing processes.
[0060] The fine adjusting unit is configured to allow the ignition
position to remain unchanged when the current reflection
coefficient |.GAMMA.| is no greater than the ignition reflection
coefficient |.GAMMA.t|, perform adjustment in real time based on
the current load impedance to realize impedance matching, and set
the current position as the matching position.
[0061] The switching unit is configured to switch, in different
pulse time durations (i.e., a high voltage level period and a low
voltage level period) of the same subsequent pulse period after
impedance matching is realized for the first time, between the
ignition position and the matching position, thereby realizing
impedance matching in different pulse periods.
[0062] As such, when at the ignition position and the current
reflection coefficient |.GAMMA.| is no greater than the ignition
reflection coefficient |.GAMMA.t|, the pulsed RF power supply may
realize the ignition of the process gas. Later, when at the
matching position, the pulsed RF power supply may realize impedance
matching. Thus, by virtue of the switching unit, in the high
voltage level period of each subsequent pulse period after the
impedance matching is realized for the first time, repeat matching
to repeatedly adjust the load impedance by automatic frequency
sweeping may no longer needed as described in existing
technologies, and impedance matching may be realized by simply
switching the ignition position to the matching position. Further,
in the low voltage level period of each subsequent pulse period
after the impedance matching is realized for the first time, the
matching position may be switched to the ignition position.
Accordingly, ignition may be ensured to be realized directly in the
high voltage level period of the next pulse period, and re-matching
may be realized by switching the ignition position to the matching
position. Accordingly, in the present disclosure, in the high
voltage level period of each subsequent pulse periods after
impedance matching is realized for the first time, the matching
time is the switching time that switches the ignition position to
the matching position. The matching time is a period of time used
by the matching process to change from an unmatched state to a
matched state. By comparing the prior art and embodiments of the
present disclosure, in each subsequent pulse period after the
impedance matching is achieved for the first time, the matching
time in the prior art is found to be relatively long because a
relatively long time is needed to realize matching by automatic
frequency sweeping and repeated adjustment of the load impedance.
However, in embodiments of the present disclosure, repeated
adjustment of the load impedance may no longer be needed, and
matching may be realized by simply switching each component from
the ignition position to the matching position. Accordingly, the
matching time is short, and the matching efficiency is high, such
that the stability of the process and the utilization of the pulsed
RF power supply may be improved.
[0063] In one embodiment, the impedance matching device further
includes a control module, a calculation module and a reflection
coefficient determination module. The calculation module is
configured to calculate the current load impedance and the current
reflection coefficient |.GAMMA.| of the pulsed RF power supply in
real time, send the current load impedance to the coarse adjusting
unit and the fine adjusting unit, and send the current reflection
coefficient |.GAMMA.| to the reflection coefficient determination
module. The reflection coefficient determination module is
configured to determine whether or not the current reflection
coefficient |.GAMMA.| is no greater than the ignition reflection
coefficient |.GAMMA.t|. If the current reflection coefficient
|.GAMMA.| is determined to be greater than the ignition reflection
coefficient |.GAMMA.t|, a first identification signal (e.g., a high
voltage level "1") is sent to the control module, otherwise, a
second identification signal (e.g., a low voltage level "0") is
sent to the control module. The control module is configured to
trigger the coarse adjusting unit upon receival of the first
identification signal, and trigger the fine adjusting unit upon
receival of the second identification signal.
[0064] Further, the coarse adjusting unit includes an adjustable
capacitor and/or an adjustable inductor. Under such situation, the
coarse adjusting unit is configured to adjust the adjustable
capacitor and/or the adjustable inductor in real time based on the
current load impedance sent by the calculation module and adjust
the current reflection coefficient |.GAMMA.| to be no greater than
the ignition reflection coefficient |.GAMMA.t|. Accordingly, the
process gas may be ignited, and the current position(s) of the
adjustable capacitor and/or the adjustable inductor may be set as
the ignition position(s). To adjust the adjustable capacitor and/or
the adjustable inductor, the coarse adjusting unit further includes
a motor, etc., and the motor may be a stepper motor. As shown in
FIG. 8, the disclosed coarse adjusting unit includes adjustable
capacitors C1 and C2; a driving motor M1 is connected to an
adjustment terminal of the adjustable capacitor C1 for adjusting
the adjustable capacitor C1; and a driving motor M2 is connected to
an adjustment terminal of the adjustable capacitor C2 for adjusting
the adjustable capacitor C2.
[0065] The fine adjusting unit includes a fixed capacitor and/or a
fixed inductor, and an on-off switch connected in series therewith.
As shown in FIG. 8, the fine adjusting unit includes two branches,
where one branch includes an on-off switch K1 and a fixed capacitor
C11 connected in series, and the other branch includes an on-off
switch K2 and a fixed capacitor C12 connected in series. The on-off
switches K1 and K2 include an electronic switch such as a diode or
relays. Under such situation, the fine adjusting unit is configured
to control on or off of the on-off switches (K1 and K2) in real
time based on the current load impedance sent by the calculation
module to realize impedance matching. Further, the state of the
on-off switches (K1 and K2) that realizes impedance matching is set
to be matching on-off state (also referred to as a "matching
position"). For example, if the on-off switch K1 is turned on and
the on-off switch K2 is turned off when the impedance matching is
realized, the matching on-off status (matching position) is that
the on-off switch K1 is turned on and the on-off switch K2 is
turned off.
[0066] Further, the impedance matching device further includes a
storage module, and the storage module is configured to store the
matching position(s) when the fine adjusting unit performs
real-time adjustment based on the current load impedance to realize
impedance matching. More specifically, the on-off status of the
on-off switches K1 and K2 is stored.
[0067] Preferably, in one embodiment, the impedance matching device
further includes a pulse period determination module, and the pulse
period determination module is configured to determine whether or
not a current moment is in a high voltage level period of the pulse
period when matching has not been realized. If the current moment
is determined to be in a high voltage level period of the pulse
period when matching has not been realized, the coarse adjusting
unit is triggered, otherwise, the current position remains to be
unchanged. That is, C1, C2, K1 and K2 each maintains a
corresponding position. As such, when the disclosed impedance
matching device has not realized impedance matching for the first
time, the coarse adjusting unit is triggered if the current moment
is in the high voltage level period, and no operation is performed
if the current moment is in the low voltage level period. Thus,
"blind adjustment" may be avoided compared to that in the prior art
in which the execution mechanism is controlled to adjust, in the
low voltage level period, the impedance adjustable element based on
the load impedance at the last time point of the high voltage level
period when the impedance matching has not been realized for the
first time. Thus, the occurrence of the over-adjustment phenomenon
may be avoided, thereby improving the matching efficiency of
achieving the impedance matching for the first time.
[0068] Further, in one embodiment, the pulsed RF power supply has
an automatic frequency-sweep mode for performing automatic
impedance matching when determining whether or not the current
moment is in the high voltage level period before the impedance
matching is realized for the first time. That is, the pulse
frequency of the pulsed RF power supply is automatically adjusted
to perform matching. It can be understood that, by using the pulsed
RF power supply to perform automatic frequency-sweep matching in
the high voltage level period of the pulse period, not only the
matching efficiency is improved, but also the matching accuracy is
improved.
[0069] Hereinafter, how the impedance matching device provided by
the present disclosure improves the impedance matching rate is
validated by experiments. In this experiment, the reaction chamber
shown in FIG. 3 is used, the second impedance matching device uses
the impedance matching device provided by the above embodiment of
the present disclosure, and other parameters are the same as that
in the prior art.
[0070] Under the aforementioned conditions, if the current
reflection coefficient |.GAMMA.| is greater than the ignition
reflection coefficient |.GAMMA.t| at the very beginning of the
matching, descriptions will be given with reference to FIG. 9, FIG.
10 and FIG. 11.
[0071] As shown in FIG. 9, FIG. 10 and FIG. 11, when the pulsed RF
power supply is not turned on, the load impedance of the pulsed RF
power supply is an impedance induced by the interference signal, as
represented by the impedance zone A outside of the circle in the
Smith chart. After the pulsed RF power supply is turned on, the
pulse synchronous signal is sent to the pulse period determination
module, and the pulse period determination module determines in
real time whether or not the current moment is the high voltage
level period of the first pulse period. On one hand, if the pulse
period determination module determines that the current time period
is the high voltage level period of the first pulse period, the
pulsed RF power supply performs automatic frequency-sweep matching.
Further, the calculation module starts to calculate the current
load impedance and the current reflection coefficient |.GAMMA.| in
real time, send the current load impedance to the coarse adjusting
unit and the fine adjusting unit, and send the current reflection
coefficient |.GAMMA.| to the reflection coefficient determination
module. During the whole high voltage level period T1, if the
reflection coefficient determination module determines in real time
that the current reflection coefficient |.GAMMA.| from the
calculation module is greater than the ignition reflection
coefficient |.GAMMA.t|, the ignition of the process gas in the
reaction chamber is indicated as not realized, and the reflection
coefficient determination module sends the first identification
signal "1" to the control module. When the control module receives
the first identification signal "1", the coarse adjusting unit is
triggered, such that the coarse adjusting unit adjusts the
adjustable capacitors C1 and C2 in real time based on the current
load impedance from the calculation module. That is, matching is
performed by using a "motor matching mode". In such matching
process, the load impedance of the pulsed RF power supply moves
from the non-ignited impedance zone (not shown in FIG. 11) towards
the matched impedance zone C. Further, in the matching process, the
on-off switches K1 and K2 do not move and are in the initial on-off
status.
[0072] On the other hand, if the pulse period determination module
determines in real time that the current time period is the low
voltage level period of the first pulse period, the current
positions of the adjustable capacitors C1 and C2 remain unchanged
and a next pulse period is waited, such that the high voltage level
of the next pulse period continues to move towards the impedance
matching zone C. By then, the load impedance of the pulsed RF power
supply is located in the impedance zone D and is the coupling
signal impedance of the inductance coil.
[0073] If the pulse period determination module determines that the
current time period is the high voltage level period of the second
pulse period, the pulsed RF power supply performs automatic
frequency-sweep matching. Further, the calculation module starts to
calculate the current load impedance and the current reflection
coefficient |.GAMMA.| in real time, sends the current load
impedance to the coarse adjusting unit and the fine adjusting unit,
and sends the current reflection coefficient |.GAMMA.| to the
reflection coefficient determination module. If the reflection
coefficient determination module determines, in real time, that the
current reflection coefficient |.GAMMA.| from the calculation
module is greater than the ignition reflection coefficient
|.GAMMA.t| during the time period T2, ignition is indicated as
having not been realized in the reaction chamber. Further, the
reflection coefficient determination module sends the first
identification signal "1" to the control module. Upon receival of
the first identification signal "1" sent from the determination
module, the coarse adjusting unit is triggered, the "motor matching
mode" is used to continue matching, and the load impedance
continues to move towards the impedance matching zone C. If the
reflection coefficient determination module determines that the
current reflection coefficient |.GAMMA.| from the calculation
module is no greater than the ignition reflection coefficient
|.GAMMA.t| at a time point t2, ignition in the reaction chamber is
indicated as being realized. By then, the current load impedance
moves to the impedance zone B corresponding to the reaction chamber
that realizes ignition, and the reflection coefficient
determination module sends the second identification signal "0" to
the control module. Upon receival of the second identification
signal "0", the fine adjusting unit is triggered, such that the
current positions (i.e., the ignition positions) of the adjustable
capacitors C1 and C2 remain unchanged. The on-off switches K1 and
K2 are controlled to be on or off in real time based on the current
load impedance sent from the calculation module. That is, the
matching is performed by using a "switch matching mode", where the
impedance matching is achieved after the on-and-off response time
T3 (i.e., a switching time) of the on-off switches K1 and K2. By
then, the current load impedance rapidly moves from the impedance
zone B to the impedance matching zone C near the impedance matching
point after the on-off response time T3. By then, the load
impedance may move to the impedance matching point because of the
automatic frequency-sweep matching of the pulsed RF power supply.
Further, when the impedance matching is realized by using the
"switch matching mode", the storage module stores the current
on-and-off states of the on-off switches K1 and K2 as the matching
on-off states.
[0074] If the pulse period determination module determines in real
time that the current time period is the low voltage level period
of the second pulse period, although impedance matching has been
realized in the high voltage level period of the second pulse
period, impedance matching needs to be re-performed in a next pulse
period. Thus, the ignition positions of the adjustable capacitors
C1 and C2 remain unchanged, and the on-off switches K1 and K2 are
switched from the matching on-off states to the initial on-off
states. In such low voltage level period, the load impedance of the
pulsed RF power supply is located in the impedance zone D and is
the coupling signal impedance of the inductance coil.
[0075] If the pulse period determination module determines that the
current time period is the high voltage level period of the third
pulse period, the pulsed RF power supply performs automatic
frequency-sweep matching. The calculation module calculates the
current load impedance and the current reflection coefficient in
real time, sends the current load impedance to the coarse adjusting
unit and the fine adjusting unit, and sends the current reflection
coefficient to the reflection coefficient determination module.
Because the adjustable capacitors C1 and C2 are at the ignition
positions and the on-off switches K1 and K2 are in the initial
on-off states, the reflection coefficient determination module
determines that the current reflection coefficient |.GAMMA.|
transmitted from the calculation module is no greater than the
ignition reflection coefficient |.GAMMA.t|. By then, it means that
ignition in the reaction chamber is realized, the load impedance is
located in the impedance zone B, and the reflection coefficient
determination module sends the second identification signal "0" to
the control module. Upon receival of the second identification
signal "0", the control module triggers the fine adjusting unit to
keep the ignition positions of the adjustable capacitors C1 and C2
to be unchanged and directly control the on-off switches K1 and K2
to switch from the initial on-off states to the matching on-off
states. The impedance matching is realized after the switching time
T3 of the on-off switches K1 and K2, and the load impedance rapidly
moves from the impedance zone B to the impedance matching zone C
near the impedance matching point after the period of time T3, and
the load impedance is adjusted to be located at the impedance
matching point by the automatic frequency-sweep matching of the
pulsed RF power supply.
[0076] If the pulse period determination module determines that the
current time period is the low voltage level period of the third
pulse period, although the impedance matching has been achieved in
the high voltage level period of the third pulse period, the
impedance matching needs to be re-performed in a next pulse period.
Thus, the ignition positions of the adjustable capacitors C1 and C2
are kept unchanged, and the on-off switches K1 and K2 are switched
from the matching on-off states to the ignition on-off states. In
such low voltage level period, the load impedance of the pulsed RF
power supply is located in the impedance zone D and is the coupling
signal impedance of the inductance coil.
[0077] Situations in the high and low voltage level periods of the
fourth pulse period and each subsequent pulse period are the same
as the situations in the high and low voltage level periods of the
third pulse period, and such rules are maintained until the process
ends.
[0078] If the current reflection coefficient |.GAMMA.| is no
greater than the ignition reflection coefficient |.GAMMA.t| at the
very beginning of the matching, the description are given
hereinafter with reference to FIG. 9, FIG. 11 and FIG. 12.
[0079] As shown in FIG. 9, FIG. 11 and FIG. 12, when the pulsed RF
power supply is not turned on, the load impedance of the pulsed RF
power supply is located in the impedance zone A outside of the
circle in the Smith chart, and is an impedance induced by the
interference signal. After the pulsed RF power supply is turned on,
the pulse synchronous signal is sent to the pulse period
determination module, and the pulse period determination module
determines in real time whether or not the current time period is
the high voltage level period of the first pulse period. On one
hand, if the pulse period determination module determines that the
current time period is the high voltage level period of the first
pulse period, the pulsed RF power supply performs automatic
frequency-sweep matching. Further, the calculation module starts to
calculate the current load impedance and the current reflection
coefficient |.GAMMA.| in real time, send the current load impedance
to the coarse adjusting unit and the fine adjusting unit, and send
the current reflection coefficient |.GAMMA.| to the reflection
coefficient determination module. If the reflection coefficient
determination module determines, at a time point t2, that the
current reflection coefficient |.GAMMA.| is no greater than the
ignition reflection coefficient |.GAMMA.t|, it means that ignition
in the reaction chamber is realized at the time point t2 and the
current impedance is located in the impedance zone B. The
reflection coefficient determination module sends the second
identification signal "0" to the control module. Upon receival of
the second identification signal "0", the control module triggers
the fine adjusting unit to maintain the ignition positions (i.e.,
initial positions) of the adjustable capacitors C1 and C2 to be
unchanged. Further, the on-off switches K1 and K2 are controlled to
be on or off in real time based on the current load impedance sent
from the calculation module. That is, the matching is performed by
using the "switch matching mode", and the impedance matching is
realized after the on-off response time T3 of the on-off switches
K1 and K2. By then, the load impedance rapidly moves from the
impedance zone B to the impedance matching zone C near the
impedance matching point after the period of time T3, and the load
impedance is adjusted to be at the impedance matching point by the
automatic frequency-sweep matching of the pulsed RF power supply.
Further, when the "switch matching mode" is used to realize
impedance matching, the storage module stores the current on-off
states of the on-off switches K1 and K2 as the matching on-off
states.
[0080] On the other hand, if the pulse period determination module
determines in real time that the current time period is the low
voltage level period of the first pulse period, although impedance
matching has been realized in the high voltage level period,
impedance matching needs to be re-performed in a next pulse period.
Thus, the positions of the adjustable capacitors C1 and C2 are kept
unchanged, and the on-off switches K1 and K2 are switched from the
matching on-off states to the initial on-off states. Further, in
the low voltage level period, the load impedance of the pulsed RF
power supply is located in the impedance zone D and is the coupling
signal impedance of the inductance coil.
[0081] If the pulse period determination module determines that the
current time period is the high voltage level period of the second
pulse period, the pulsed RF power supply performs automatic
frequency-sweep matching. Further, the calculation module
calculates the current load impedance and the current reflection
coefficient |.GAMMA.| in real time, sends the current load
impedance to the coarse adjusting unit and the fine adjusting unit,
and sends the current reflection coefficient |.GAMMA.| to the
reflection coefficient determination module. Because the adjustable
capacitors C1 and C2 are at the ignition positions and the on-off
switches K1 and K2 are in the initial on-off states, the reflection
coefficient determination module directly determines that the
current reflection coefficient |.GAMMA.| from the calculation
module is no greater than the ignition reflection coefficient
|.GAMMA.t|. By then, ignition in the reaction chamber is indicated
as having been realized and the load impedance is located in the
impedance zone B. The reflection coefficient determination module
sends the second identification signal "0" to the control module.
Upon receival of the second identification signal "0", the control
module triggers the fine adjusting unit to keep the ignition
positions of the adjustable capacitors C1 and C2 to be unchanged.
Further, the control module directly controls the on-off switches
K1 and K2 to switch from the initial on-off states to the matching
on-off states. The impedance matching is realized after the
switching time T3 of the on-off switches K1 and K2, and the load
impedance rapidly moves from the impedance zone B to the impedance
matching zone C near the impedance matching point after the
switching time T3, and the load impedance is adjusted to be at the
impedance matching point via the automatic frequency-sweep matching
of the pulsed RF power supply.
[0082] If the pulse period determination module determines that the
current time period is the low voltage level period of the second
pulse period, although the impedance matching has been realized in
the high voltage level period of the second pulse period, the
impedance matching needs to be re-performed in a next pulse period.
Thus, the positions of the adjustable capacitors C1 and C2 remain
unchanged, such that the on-off switches K1 and K2 are switched
from the matching on-off states to the initial on-off states. In
the low voltage level period, the load impedance of the pulsed RF
power supply is located in the impedance zone D and is the coupling
signal impedance of the inductance coil.
[0083] Situations in high and low voltage level periods of the
third pulse period and each subsequent pulse period are the same as
the situations in the high and low voltage level periods of the
second pulse period, and the rules are maintained until the process
ends.
[0084] By comparing FIG. 4, FIG. 10 and FIG. 12, existing
technologies in FIG. 4 is found to, after impedance matching is
realized for the first time, realize impedance matching after a
relatively long time T for each subsequent pulse period. However,
in embodiments of the present disclosure shown in FIG. 10 and FIG.
12, after impedance matching is realized for the first time,
impedance matching may be realized after the switching time or
on-off response time T3 for each subsequent pulse period, and
T3<T. As such, the matching efficiency of the pulsed RF power
supply provided by embodiments of the present disclosure may be
improved.
[0085] It should be noted that, in one embodiment, the matching
network of the impedance matching device has a circuit structure of
an L shape, but the present disclosure is not limited thereto. In
practical applications, circuit structures of the matching network
may also include an inverted-L shape, a T shape, or a .pi. shape,
etc.
[0086] It should further be noted that, although the fine adjusting
unit in the present disclosure includes a fixed capacitor and/or a
fixed inductor and an on-off switch connected in series therewith,
and the switching between the ignition position and the matching
position is realized by the on or off of the on-off switch.
However, the present disclosure is not limited thereto. In
practical applications, other methods may also be used to rapidly
switch between the ignition position and the matching position.
Further, although a fixed capacitor and an on-off switch connected
in series therewith are provided respectively in two branches of
the fine adjusting unit in the present disclosure, the present
disclosure is not limited thereto. In practical applications, each
branch may include a plurality of capacitors and/or inductors and a
plurality of on-off switches connected in series therewith, and the
reactance value of the fine adjusting unit is changed via a
combination of the on/off states of each on-off switch.
[0087] It should further be noted that, the impedance matching
device provided by the present disclosure does not limit the RF
frequency of the pulsed RF power supply 30. For example, the RF
frequency may be 400 kHz, 2 MHz, 3 MHz, 27 MHz, 40 MHz, or 60 MHz,
etc. Further, the pulse frequency and the pulse duty cycle of the
pulsed RF power supply 30 are also not limited. For example, the
pulse frequency may be within 1 MHz, and the pulse duty cycle may
be any value less than 1.
[0088] It can be understood that the foregoing implementations are
merely exemplary implementations used for describing the principle
of the present disclosure, but the present disclosure is not
limited thereto. Those ordinarily skilled in the art may make
various variations and improvements without departing from the
spirit and essence of the present invention, and these variations
and improvements shall all fall within the protection scope of the
present disclosure.
* * * * *